1. Field of the Invention
This invention relates to semiconductor light-emitting or luminescent devices such as light emitting diodes, semiconductor laser devices and the like, which devices are capable of emitting light or oscillation over a wide wavelength range of from blue light to ultraviolet region.
2. Description of the Prior Art
As is well known in the art, light emitting diodes are potential light emitting parts, and red light emitting devices using AlGaAs and green light emitting devices using GaP have been now widely employed as display devices. At present, there is a great demand for blue light emitting devices, which can stand practical use, for multiple coloration purposes. However, such blue light emitting devices have not been in use yet.
On the other hand, in the fields of semiconductor laser devices, semiconductor laser devices using III-V semiconductors (compounds of Groups III-V of the periodic table) such as AlGaAs/GaAs have been actually employed in optical disks for signal pickup purposes. If the oscillation wavelength of the semiconductor laser device for signal pickup can be shortened, the quantity of information memorizable in the disk can be increased, enabling one to enhance the information processability of the optical disk. In the fields of laser printers, the shortening of the oscillation wavelength can improve the sensitivity of photosensitive material and increase the printing speed. Thus, in order to improve the performance of information processing apparatus and other hose-use instruments, it is necessary to shorten the oscillation wavelength of semiconductor laser devices. To this end, the active layer of the semiconductor laser device should make use of a direct transient III-V semiconductive compound having a great band gap. Among direct transient III-V semiconductive compounds, those materials having a great forbidden band gap include AlGaInP. When this material is used as the active layer, the oscillation wavelength ranges from 580 to 690 nm. As a material having a greater band gap among the direct transient semiconductive compounds, there is known Zn(SSe) which is a II-VI semiconductor. The use of the above semiconductor to constitute a double heterostructure provides the possibility of realizing a semiconductor laser device capable of emitting light with a short wavelength. At present, because of the difficulty in controlling the p-type conduction, any semiconductor laser device using Zn(SSe) semiconductors have not been in use yet.
On the other hand, the possibility of fabricating p-n junction light-emitting devices using combinations of n-type II-VI semiconductors (i.e. semiconductive compounds of Group II-VI of the periodic table) and p-type chalcopyrite compounds is known, for example, in J. Appl. Phys., 45 (1974) 246, by Sigurd Wagner and Technical Report of the Society of the Electron Information Communication, CPM88-5, 3(1988), by Nozomu Tsuboi et al. According to these papers, heterojunction diodes are fabricated using combinations of II-VI semiconductors and chalcopyrite compounds, both having a great forbidden band gap. In the former paper, it is stated that green light emission is attained at 77.degree. K. by the use of the combination of CdS--CuGaS.sub.2. In the latter paper, it is stated that yellowish orange light is emitted at room temperature by the use of the combination of ZnCdS--CuAlGaS.sub.2.